Electromagnetic sounding-board actuator



Dec. 25, 1928. 1,696,305-

M; R. HUTCHISON ELEQTROMAGNETIC SOUNDING BOARD ACTUATOR Filed April 1,1927 INVENTOR QAZW ATTORNEY Patented Dec. 25, 1928.

l UNITED STATES PTENT QFFICE.

' MILLER iznnsn nuromsoiv, or wear ORANGE, NEW JERSEY, AssIenon, BYmssnn ASSIGNMENTS, TO ACOUSTIC rnonucrs COMPANY, or NEW YORK, N. Y., A.003.-

PORATION OF DELAWARE.

ELECTROMAGNETIC SOUNDING-BOARD ACTUATOR.

Application filed s in 1, 1927.

This invention relates to new and useful improvements in electromagneticsounding board actuators such as are used for transforming impulses ofelectric currents into i sound waves.

Its object is to provide a simple device of great efliciency and toprovide a so-called 7 i so i other device which also embodies thisinsound propagators and which are supported vention.

In Fig. 1, 10 and 11 designate two members which are resonant soundingboards or in substantially parallel relation in a base 12.

v e A bridge, 13 spans the members 10 and 11 1 across the top and may besecured to them in any suitable manner. 14 is aflexible suspensionsupport between the bridge 13 and the electromagnetic unit 15.

v The electromagnetic unit is shown somewhat in detail in Fig. 2. Itcomprises a body having a permanent magnet to which are rigidly ailixedpole shoes 21 and 22 between which is a coil 23. A vibratory armature 24is flexibly supported, onthe permanent mag net by a spring 25 whichholds it between the ma etic pole shoes. 26 is a push-pull .rod. whichforms a rigid connection between the permanent ma net 20 and member 10.

. 27 is a push-pull rod which forms a rigid connection between armature24 and member 11. The points at which the rods 26 and 27 are connectedto the sound propagators are considerably above the center of theirlength. They are shown in'Fig. 1 as located about one sixth of. thelength of the members 10 and 11, as I have found this to be an eifectiveposition.

In operation, the balance of the parts is disturbed by a current whichflows through the coil 23. WVhen such a current causes the which formSeriaI No. 180,183.

armature 24 to be attracted by pole shoe 21 and repelled by pole shoe22, this will cause a movement of the member 10 to the left. Thereaction to this force will effect a simultaneousmovement of the body ofthe electro' magnetic unit 15 and of the member 11 t0 the right.)bviously magnetic pulls in the opposite direction will move the members10 and 11 in the other directions. Thus any vibrations imparted by theelectromagnetic unit 15 to the sound propagators 10 and 11 will alwaysbe simultaneous and opposite The results attained by such anorganization in the production of sound waves are highly effective anddesirable.

The same general effect may be obtained with a loud speaker of thedouble con-e type, such as illustrated in Fig. 3. In this case the base12 supports two cones, 10 and 11 the apexes of which are connected byrods 26 and 27 with the armature and body respectively of anelectromagnetic unit 15 which is flexibly suspended by a support 14'from the upper peripheries of the cones.

The electro-responsive unit, therefore. comprises two vibratory memberswhich move relatively but in opposite direct-ions. Because of thedifl'crence in mass between the armature and the body, their movementsare not equal. As a result the armature with its attached member 10, andthe bod with its attached member .11, are unequally responsive toelectric current variations of a given frequency. Furthermore, thearmature and its attached member 10. are more responsive to currentvariations of certain frequencies than are the body and its attachedmember 11, and the body and member 11 are more responsive to currentvariations of an entirely different frequency. Consequently theorganization as a whole serves to transform current variations over anextremely large difference of frequencies, into sound Waves of acorrespondingly wide range.

Two embodiments of this invention have been illustrated and described toshow that it is not limitedto any specific form or con struction and Iintend no limitations other than those imposed by the appended claims.

What I claim is:

1. A pair of vibratory sound propagators in bpposed relation, anelectromagnetic unit flexibly supported between said ropagators'comprising two relatively movable parts, a

connectionbetween one of the propagators and one of said parts, andanother connection between the other of the propagators and the other ofsaid parts.

2. A pair of vibratory sound propagators in 0 posed relation, anelectromagnetic unit fles'i ly supported between said propagatorscomprising two relatively movable parts, a rigid connection between oneof the propagators and one of said parts, and another rigid connectionbetween the other of the propagators and the other of said parts, saidconnections bein in alinement.

3. A pair of vibratory sound propagators in o posed relation, anelectromagnetic unit flexibly supported between said propagatorscomprlsing two relatively movable parts, a rigid connection between oneof the propagators and one of said parts, and another rigid connectionbetween the other of the propagators and the other of said parts, saidconnections being in alinement and offset from the center of saidpropagators.

4, A pair of sound propagators in o posed relation, an 1 electromagneticunit exibly supported between said propagators comprising two relativelymovable parts of unlike mass, a connection between one of the proagators and one of said parts, and anot er connection between the otherof the propagators and the other of said parts.

5. A pair of sound propagators in o posed relation, an electromagneticunit flexib y supported between said ropagators comprising tworelatively movab e parts of unlike mass, a rigid connection between oneof the pro agators and one of said parts, and anot er rigid connectionbetween the other of the propagators and the other of said parts, saidconnections being in alinement.

6. A pair of sound propagators in o )posed relation, an electromagneticunit flexibiy supported between said propagators comprising tworelatively movable parts of unlike mass, a rigid connection between oneof the pro agators and one of said parts, and anot er rigid connectionbetween the other of the propagators and the other of said parts, saidconnections being in alinement and offset from the center of saidpropagators.

In witness whereof, I have hereunto set my handthis th day of March,1927.

MILLER REESE HUTCHISON.

